Past studies have quantitated the effect of mass air flow in animal laboratories and developed methods for optimal use using an assay system of polyoma virus infection developed in this laboratory. Other parameters included environmental impact, animal growth, cost-effectiveness and engineering feasibility. Proposed studies will be performed in a mass air flow room and a conventionally ventilated room with airborne polyoma virus to determine if more economical designs of mass air flow can be developed that are as efficient as presently available systems by using less expensive filters and a lower air velocity when no personnel are in the mass air flow room. The efficiency of other preventives of airborne infections, namely, increased turbulent ventilation, elimination of bedding and ultraviolet irradiation will be determined relative to mass air flow. Cost analysis will be performed in all studies using technician hours and kilowatt hours utilized per week, among other factors. The results of these studies will increase cost-effectiveness of many methods of ventilation.